The present invention relates to a curved formwork system with varying curvature, the purpose of which is to enable the construction of curved walls in building and civil work, having characteristics that solve the need for a versatile and functional formwork.
The formwork that is the object of the invention allows a great simplicity in its assembly and curvature, involving minimal labor expenditure.
The special characteristics of the system provide the formwork with great sturdiness that allows numerous re-usages with configurations differing in radius and height.
Many modular curved formwork types are known that are used by the applicant firm and by many others, such as PERI, DOKA, Hxc3x9cNNEBECK, MEVA, MECANOTUBO, ALSINA, PASCHAL, etc., such that the formworks used by many of these companies comprise a face sheet on which a fixed number of girders are attached in the form of vertical ribs, so that on said girders or vertical ribs are placed more-or-less ingenious systems of tensioning devices and stiffeners in order to curve the formwork panel and support the concrete pressure respectively.
As regards the lateral union of the formwork panels, each brand or manufacturer uses its own profile or attachment system, whether it be a clip, lock or the like.
Among specific systems used to make circular formworks can be cited those described in Spanish Patents 534.744 and 2000777, wherein the former describes a formwork system for curved surfaces with two formwork faces or liner elements conveniently separated to form the mold, complemented by trapezoidal profiles attached to the external face of said elements, jointed to which profiles are attachment elements or parts that are joined to each other by tensioning devices comprised of a bushing which screw onto two segments with opposite threads and are joined to the ends of the aforementioned parts attached to the trapezoidal profiles, so that turning these bushings in one sense or the other results in pulling on or separating the consecutive trapezoidal profiles, and thereby the curvature of the elements that make up the formwork face or liner.
In the second patent cited, No. 2000777, another formwork is described for circular or polygonal constructions in which exists a series of segments related to each other by their ends, forming beams that are placed outside of the elements that make up the formwork face or liner, with tensioning devices provided between each two beam segments that when actuated perform the same function as in the previous case, that is, separating or approximating the segments of beams, which as they are attached to the formwork faces or liners cause the curvature or angle between segments.
In addition may be mentioned European Patent 0 514 712, which describes a formwork for surfaces with differing curvature based on the same principles as the previous one, in which the elements that are mounted on the trapezoidal profiles instead of being individually attached to said profiles have the special characteristic that each element defines a stiffener mounted between two trapezoidal profiles, further forming a support for a bar that joins to each other the two faces that form the formwork.
In this European Patent, said stiffeners incorporate on one of their ends an adjustment spindle that is related to a shaft or pin, and by a suitable part it is hinged to the trapezoidal profile, with actuation of said spindle causing the separation or approximation of the two parts that connect the stiffener to the two consecutive trapezoidal profiles, and therefore giving them a tendency to approach or separate from each other, thus producing the curvature of the corresponding formwork face or liner.
The two stiffeners of each strap are joined by intermediate adjustable tensioning devices that are used to adjust uniformly the curvature of the panel in the central zone. Additionally, the panel curvature is completed by end tensioning devices that adjust the roundness of the edges of the formwork panel.
The main drawback of the formwork described in said European Patent is that a large number of elements must be acted upon to curve the panel, firstly the stiffener spindles must be adjusted, then the intermediate tensioning devices and finally the end tensioning devices, thus requiring a large amount of time and/or labor to adjust the curvature of the entire formwork.
A further disadvantage is that the curved formwork system of this patent uses different stiffener-spindle-nut assemblies depending on whether it is used for the inner side of the curvature or the outer side, thus complicating the assembly of the formwork.
The formwork system herein disclosed, being based on those cited in the previous section, presents a number of special characteristics or improvements that provide new functions, improved results and optimized functionality and usefulness of the formwork itself.
More specifically, one of the improvements object of the invention is that the formwork face or liner is comprised of a metal sheet on the outer side of which are welded five vertical trapezoidal profiles, and on each end of the sheet is an edge profile, with the stiffeners and the trapezoidal and edge profiles joined by intermediate swiveling elements that can move and turn with respect to the stiffeners. Each swiveling support is comprised of a pair of triangular plates, hereinafter referred to as the triangle, with central and end triangles determined depending on their position.
The central triangles are joined by two of their vertices to two consecutive trapezoidal profiles, while the third vertex is joined to one of the ends of a stiffener, so that one of the unions to the trapezoidal profiles is hinged and the other is such that it can slide somewhat, thereby allowing the triangle to both turn and slide with respect to the stiffener.
The end triangles are joined by one of their vertices to a trapezoidal profile and by another vertex to the edge profile provided on the end of the sheet, with a hinged union at the edge profile and a sliding union at the trapezoidal profile.
In addition, each stiffener is joined to two consecutive triangles, hinged to one and joined to the other so that it can slide, by means of a tensioning mechanism whose operation will be described below.
Thus, mounted on each stiffener is a tensioning mechanism comprised of a spindle and a moving nut, joined to a transverse shaft that is connected to the two plates that form the corresponding triangle, with the spindle""s motion limited on one side by the spindle head and on the other by a nut attached to the other end, which elements stop against corresponding plates welded to the stiffener, so that when the outer spindle head is acted upon the moving nut will slide on it, carrying the transverse shaft and thus the triangle to cause said triangle to swivel with respect to the stiffener, while the latter pulls or pushes on the trapezoidal profiles to curve the formwork face.
In accordance with the present invention, the plate that defines a panel incorporates five vertical trapezoidal profiles, two edge profiles, two central triangle joined to the trapezoidal profiles and to one edge profiles, and two stiffeners, each of which is attached to two consecutive triangles.
With this structure it is possible to adjust the curvature of each panel by acting on the tensioning spindles of the stiffeners, which curves the entire panel, including its end and central areas, without requiring special tensioning devices or elements.
Additionally, as there are more profiles that usual and as the stiffeners act on these through swiveling triangles, a greater curvature of the panel is obtained and the formwork face is made rounder.
The system also includes a blocking mechanism that immobilizes the formwork after the desired curvature is obtained, which blocking device or mechanism consists of a threaded stud which, using two lock nuts and being fixed between the triangular plate and the trapezoidal profile, fixes and locks the panel in the curved position given to it.
In addition, between the contiguous ends of the two stiffeners of each strap is provided a central tensioning device that locks the curve in this area.
A further advantage of the system disclosed is that the stiffeners, triangles and tensioning devices used to curve the panel are the same for the inner and outer faces of the panel.
The edge profiles provided on the ends of the metal sheets that form the formwork faces also allow the collateral union of two adjacent panels by special clips provided for this purpose.
Another improvement is that the element that forms the face, that is, the metal sheet, is provided on its top and bottom edges with centering shims that are also provided on the edge profiles, allowing a vertical assembly without any problems, easily and simply.
A further improvement is that said metal sheet that forms the panel liner is provided with lower leveling legs embodied as spindles with a support base, allowing a correct setting and leveling on the floor and prevents the sheet from touching said floor.